This invention relates generally to sheet feeding devices, and more particularly, to devices commonly known as xe2x80x9cnailsxe2x80x9d used for forcing a loop or bow in a top sheet of a stack to separate the top sheet from the stack to avoid double feeding.
Many known printers utilize a stack of image receiving or printing medium sheets such as paper or transparencies in a storage tray, cassette, or the like, which sheets are picked or fed one at a time from the top of the stack to a print station. Commonly, a roller or other picker device is utilized to engage the top surface of the top sheet of the stack to push the top sheet off of the stack while the devices such as pawls or the devices occasionally known as nails or xe2x80x9ccorner nails,xe2x80x9d for their location adjacent to the leading edge corners of the top sheet, function to resist movement of the top sheet. In concert with resisting movement of the top sheet, the nails force a loop or bow in the top sheet which operates to separate it from the next succeeding sheet on the stack to prevent a double feed, that is, the feeding of both the top sheet and the next succeeding sheet or sheets. Reference for example, my U.S. Pat. No. 5,669,601, issued Sep. 23, 1997 to Eastman Kodak Company, Rochester, N.Y., which shows a representative corner nail construction. Typically, known corner nails such as that disclosed in my patent utilize gravity or a separate mechanical spring to keep the nail in contact with the corner of the top sheet. However, for some applications, gravity may be an inadequate force, or may require too large of a nail. In the alternative, use of a separate spring to bias the nail against the corner of the top sheet may be disadvantageous costwise. It has also been found desirable to minimalize friction, the occurrence of burrs on the nails, and other impediments to smooth movement between the nail and the top sheet during removal of the top sheet from the stack.
Therefore, there is a need to provide a sheet feeding device including a new corner nail construction which provides effective yet low frictional contact with a top sheet of a stack for preventing or limiting the occurrence of double feeding, is advantageous costwise, and does not rely on gravity or require a separate spring for operation.
An object of the present invention is to provide a sheet feeding device including a new nail construction which is advantageous costwise, provides effective yet low frictional contact with a top sheet of a stack for preventing or limiting the occurrence of double feeding, and which does not rely on gravity or a separate spring for operation.
With this object in view, the present invention resides in a spring nail for a sheet feeding device having one end for attaching to the sheet feeding device and a free end opposite the mounting end, the free end being disposed to engage a top sheet of a stack of sheets to be fed and exert a resilient biasing force thereagainst to form a loop or bow in the top sheet for separating the top sheet from the stack when the top sheet is removed from the stack.
The present invention also resides in a sheet feeding device including an element for supporting a stack of sheets including a top sheet to be fed, the top sheet having a top surface, and at least one spring nail having a mounting end attached to the sheet feeding device and a free end opposite the mounting end, the free end being disposed to engage and exert a resilient biasing force against the top surface of the top sheet to force a loop or bow in the top sheet for separating the top sheet from the stack when the top sheet is removed from the stack.
According to an exemplary embodiment of the present invention, one each of the spring nails is provided for engaging each leading edge corner of the top sheet.
According to another exemplary embodiment of the invention, the spring nail has an integral spring arm portion between the mounting end and the free end having properties of a spring for resiliently biasing the free end of the nail against the top sheet.
According to another exemplary embodiment of the present invention, the spring nail can comprise a wire material such as a spring wire, a metal music wire, or the like. According to another exemplary embodiment of the invention, the wire spring nail has a generally round cross-sectional shape.
According to another exemplary embodiment of the present invention, the spring nail can comprise a molded plastics material.
According to another exemplary embodiment of the present invention, the spring nail can comprise a sheet metal material.
According to still another exemplary embodiment of the invention, the free end of the spring nail has a flat surface portion positioned for engaging a leading edge of the top sheet.
A feature of the present invention is the provision of a nail having an inherent spring property for resiliently biasing it into contact with a top sheet of a stack to be fed.
Another feature of the present invention is the provision of a wire spring nail having a rounded surface for engaging a top surface of a top sheet of a stack to be fed such that less friction is present between the top sheet and the nail.
Another feature of the present invention is the provision of an effective spring nail for a sheet feeding device which eliminates the need for gravity or a separate, external spring for urging the nail into contact with a top sheet of a stack to be fed.
These and other objects, feature and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there are shown and described illustrative embodiments of the invention.